Answer:
200 nm
Explanation:
Refractive index of gasoline = 1.4
Wavelength = 560 nm
t = Thickness of film
m = Order = 1
Wavelength is given by
[tex]\lambda=\dfrac{560}{1.4}=400\ nm[/tex]
We have the relation
[tex]2t=m\lambda\\\Rightarrow t=\dfrac{m\lambda}{2}\\\Rightarrow t=\dfrac{1\times 400}{2}\\\Rightarrow t=200\ nm[/tex]
The thickness of the film is 200 nm